Samacheer Kalvi 9th Social Science Geography Solutions Chapter 4 Pdf

Samacheer Kalvi 9th Social Science Geography Solutions Chapter 4 Pdf

Tamilnadu Board Samacheer Kalvi 9th Social Science Geography Solutions Chapter 4: Tamilnadu State Board Solution Class 9 Social Science Geography Chapter 4 – Hydrosphere.

Samacheer Kalvi 9th Social Science Geography Solutions Chapter 4: Overview

Board

Samacheer Kalvi
Class

9

Subject

Social Science (Geography)
Chapter

4

Chapter Name

Hydrosphere

Samacheer Kalvi 9th Social Science Geography Solutions Chapter 4 Hydrosphere

I.) Choose the correct answer

1.) The temperature of the ocean waters generally decreases at greater depth.

a) increases

b) decreases

c) remains constant

d) none of the above

2.) Ocean currents are produced due toall the above.

a) due to rotation of earth

b) due to variation in temperature

c) due to earth’s movement

d) all the above

3.) Consider the following statements.

1.) Most of the fishing grounds occur in areas where the continental shelf is wide.

2.) Fishing is well developed in warm tropical waters.

3.) Mixing of warm and cold currents facilitates plant nutrients for fish.

4.) Inland fishing became significant in India.

a) 1 and 2 are correct.

b) 1 and 3 are correct.

c) 2,3 and 4 are correct.

d) 1,2 and 3 are correct.

Answer: Statement 1 and 3 are correct.

4.) The oceanic ridge comes into existence due to divergence of tectonic plates.

a) convergence of tectonic plates

b) divergence of tectonic plates

c) lateral movements of plates

d) stearing of plates.

5.) Which of the following indicates the correct sequence of the topography beneath the surface of the sea?

a) Continental shelf-Continental slope-Sea plain-Sea trench.

b) Continental slope-Continental shelf-Sea plain-Sea trench.

c) Sea plain-Continental slope-Continental shelf-Sea trench.

d) Continental slope-Sea plain-Continental shelf-Sea trench.

Answer: a) Continental shelf-Continental slope-Sea plain-Sea trench.

6.) Which of the following is not correctly matched?

a) Gulf Stream – Pacific Ocean

b) Labradorcurrent- North AtlanticOcean

c) Canarycurrent – Mediterraneansea

d) Mozambiquecurrent – Indian Ocean

Answer: Following is not correctly matched

a) Gulf Stream – Pacific Ocean

c) Canarycurrent – Mediterraneansea

II.) Assertion (A), Reason (R) type questions.

Directions

a) Both A and R are correct and Rexplains A.

b) Both A and R are correct but R doesnot explain A.

c) A is correct but R is false.

d) A is false but R is correct

1.) Assertion (A): Oceans are alwaysshown in blue in maps.

Reason(R): It indicates the naturalcolour of the oceans.

Answer:a) Both A and R are correct and Rexplains A.

2.) Assertion(A): Flat topped seamountsare known as Guyots.

Reason(R): All guyot features are ofvolcanic origin.

Answer:c) A is correct but R is false.

  1. Assertion(A): Submarine canyonsare deep gorges on the ocean floor.

Reason(R): They are mainly restrictedto continental shelf, slope and rise.

Answer:b) Both A and R are correct but R doesnot explain A.

4.) Assertion (A): Atolls are morecommon in the Atlantic ocean.

Reason(R): The marine population atthe depth is less.

Answer:d) A is false but R is correct.

III.) Match the following:

Answer

1.) Marianatrench                                            – Deepest point in the Pacific

2.) Great BarrierReef                                      – Australia

3.) Spring tides                                                – Second order landform

4.) Heavy rains                                                – On full and new moondays

5.) Kuroshio Current                                        – Decreases salinity in the oceans

6.) Continental slope                                        – Along the coast of Japan

IV.) Answer the following in brief:

1.) What do you mean by the termHydrosphere?

Answer:Hydrosphere means the water on the earth in various forms. More than 97% water is in oceans and around 3% water is on the land. So basically, Hydrosphere means the water content on the earth.

2.) What is hydrological cycle?

Answer: The water in the earth is always in motion and this continuous movement of water on the earth and below the surface of the earth is known as Hydrological Cycle.

3.) Mention the various relief features of ocean floor.

Answer: Relief features of ocean floor are as follow

i) Continental shelf

ii) Continental slope

iii) Continental rise

iv) Deep sea plain or Abyssal plain

vi) Oceanic deep

vii) Oceanic ridge

4.) What are the factors that generate the ocean currents?

Answer: The factors that generate the ocean current are as follow

i) Rotation of the earth.

ii) Prevailing winds

iii) Differences in temperature

iv) Differences in salinity of ocean water

5.) Write a brief note on sea waves.

Answer: Sea waves are movement of the ocean and considered to be strongest. When winds blow over the sea the waves are generated. The speed, height, duration, direction of the wave is determined by wind.

V.) Give reasons for the following:

1.) The northern hemisphere and the southern hemisphere are called land and water hemispheres respectively.

Answer:The northern hemisphere and the southern hemisphere are called land and water hemisphere respectively because the norther hemisphere having 61% land and the southern hemisphere spanned with 81% of water.

2.) Continental shelf provides good fishing ground.

Answer: Continental shelf provides good fishing ground because continental shelf are adjoining to the land mass hence they are shallower and good for fishing.

VI.) Distinguish the following:

1.) Spring tide and Neap tide.

Answer:

Spring tide

Neap tide
Spring tide occurs when the sun, moon and earth are aligned in the same line.

Neap tide occurs when the sun and the moon are at right angles.

Gravitational forces of the sun and moon pull the water this forms Spring tide.

Gravitational force work against each other causes neap tide.
Spring tide always occur on full moon and new moon days.

Neap tide occurs when the first and last quarter moon appears.

2.) Abyssal plains and Ocean deeps.

Answer:

Abyssal plains

Ocean deeps
The plains found in deep ocean floor are known as Abyssal Plains.

Ocean deeps are deep area of the ocean.

Abyssal plains extend from continental rise to the mid oceanic ridges.

Oceanic deeps cover around 7% of the total of the ocean floor.

Abyssal plains are covered by thick layer of sediments made from clay, silt and sand came with rivers.

Oceanic deeps are sediment free, many of them are V-shaped with steep sides.
Example: Abyssal hills, sea mounts, guyots, coral, atoll etc.

Example: Epicentre of the great earthquakes.

VII.) Answer in a paragraph:

1.) Write a note on continental shelf and continental slope.

Answer: Continental shelf and continental slope both are the major relief features of the ocean floor

i) Continental Shelf: Continental shelf is a shallow and gently sloping platform extended from adjoining continental land mass into the sea. The continental shelf is important because of following reasons

a) Continental shelf is shallow hence sunlight can penetrate through water. It helps to grow grass, sea weeds and plankton. This zone is also good for fishing and the Grand Banks of Newfoundland is good example of it.

b) Continental shelves also have good quantity of minerals and mineral fuels. This place is accessible for oil drilling and mining activities like Mumbai High in Arabian Sea.

ii) Continental Slope: Continental slope is steep slope descends from the edge of the continental shelf to the deep ocean-bed. Continental slope is boundary between continental crust and the oceanic crust. This area does not have any deposits hence they are steep. Deep canyons and trenches are the important characteristic of continental slope. The temperature of Continental slope is freezing due to low sunlight hence the aquatic life has slow rate of metabolism.

2.) What do you mean by ocean currents? Explain its types.

Answer: Ocean current is the movement of ocean water on the surface and at the depth in a definite direction. In the northern hemisphere ocean currents are clockwise motion and in the southern hemisphere ocean current is anti-clockwise motion. There are two types of oceanic currents Warm currents and Cold currents. When the movement of ocean currents from the high latitudes (temperate and polar zones) towards low latitudes (tropical zones) is known as cold current. For example, Labrador in Atlantic Ocean, Peruvian cold current in South Pacific Ocean.

3.) Explain the influences of the marine resources on mankind.

Answer: Marine resources are the resources found in the bottoms of the ocean or oceanic water.  Marine provides us biotic resources and abiotic resources to mankind. On these resources our society is sustained. Many types of marine organisms are used as food, medicine, cosmetics and wealth of industrial requirement. The demand of energy, minerals and water is fulfilled by oceans.

Updated: July 20, 2021 — 10:53 pm

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